Caging mechanism for gyros



Jan. 15, 1946. D. W. SMITH CAGING. MECHANISM FOR .GYROS Filed Oct. 26, 194g I 2 Sheets- Sheet i INVENTOR BY .17 iKJmz/h D. W. SMITH CAGING MECHANISM FOR GYROS I Jan. 15, 1946.

Filed Oct. 26, 1942 2 Sheets-Sheet 2 INVENTOR. 17. if. J/flZf/l/ BY I HTI'ORWEY' Patented Jan. 15, 1946 2,393,124

UNITED STATES PATENT OFFICE,

2,393,124 CAGING MECHANISM FOR Gmos Donald W. Smith, Bergenfield, N. J., assignor to Bendix Aviation Corporation, Bendix, N. .L, a corporation of Delaware Application October 26, 1942, Serial No. 463,392

' 16 Claims. (c1. 74-5) This invention relates to gyroscopic devices, such as, artificial horizons or gyro verticals, for example, and more particularly to novel apparatus for automatically and/or manually caging and centralizing such devices.

It is well known to those skilled in the art that gyroscopic devices, of the foregoing character used upon aircraft, are subject to severe damage during violent craft maneuvers unless some provision is made for locking the gyroscope whensuch maneuvers are initiated. Also, where an automatic pilot is relied upon for directing craft flight, it is desirable, during the existence Of abnormal flight conditions, to centralize and lock the gyroscope of the automatic pilot. Various devices have been provided, heretofore,.for cagin and locking gyroscopes and though they are generally suitable for the purpose intended they possess certain inherent and undesirable limitations which are overcome by the present invention.

' A further source of damage, which must be considered, is that due to the occurrence of a power failure at the supply source provided for driving the gyroscope. Whether the gyroscope be electrically orpneumatically driven, it will lose rotational speed when a power failure occurs at its supply source and consequently precess abnormally creating undueand severe strains upon the bearings, etc. It is, therefore, highly desirable that, upon the occurrence of a power failure at the driving source, the gyroscope be immediately caged and centralized to prevent it from processing and injuring its bearings.

, An object of the present invention, therefore, is to provide novel caging means for gyroscopes which automatically cage and centralize the gyroscope upon the occurrence of certain given an predetermined conditions.

Another object of the invention is to provide novel caging means for gyroscopes which operate automatically and rapidly to cage and centralize the gyroscope when the craft upon which the gyroscope is mounted exceeds a predetermined angle of craft bank or pitch.

A further object of the invention is to provide 7 novel caging'apparatus for gyroscopes which operates automatically to cage the gyroscope in case of a power failure.

Another object of the invention is o Provide a novel caging and lockin mechanism for pneumatically or electrically driven gyroscopes which operates automatically to cage and centralize the gyroscope in case of a power failure either at the pressure source or the electrical source provided for driving the gyroscope.

A further object of the invention is to provide a novel artificial horizon or gyro vertical having caging means therefor which operate automatically either during a power failure or during violent craft maneuvers.

upon the existence of certain predetermined conditions without interfering with the manual caging control.

Another object is to provide a novel caging and locking apparatus for gyroscopic devices which is operable at all times to cage and lock the gyroscope whether it be spinning or not.

The above and further objects and novel fea- I tures of the invention will appear more fully from the following detailed description when the same is read in connection with the accompanyin drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition of the limits of the invention.

In the drawings wherein like reference char= acters refer to like parts throughout the several views,

Figure 1 is an exploded perspective view, partially schematic and partially in section, of one form Of a gyroscopic device embodying the subject matter of the present invention;

Figure 2 is a schematic view illustrating a detail of the structure of Figure 1;

Figure 3 is a perspective view illustrating the circuit bridging element of the structure of Figure 1; and,

Figure 4 is a schematic view illustrating a further detail of the structure of Figure l.

The novel apparatus of the present invention is illustrated in Figure 1 as applied to an artificial horizon gyro having a rotor (not shown), which may be driven either pneumatically or electrically, mounted within a casing it for spinning about a normally vertical axis. The rotor casing is mounted for oscillation about a horizontalv grees of freedom and the instrument, when mounted on a craft. has its outer trunnions i4 and i5 arranged parallel to the longitudinal craft axis and inner trunnions l2 and I3 parallel with the craft's transverse axis. The rotor spin axis is maintained vertical by any of well known erection means, suchas, for example, that shown in the United States patent to Robert Alkan, 2,159,118 issued May 23, 1939.

For carrying out the objects of the present invention, rotor casing i is provided with a caging pin IB secured to the bottom of the casing, the pin projecting downwardly with its longitudinal axis arranged to be at all times coaxial with the rotor spin axis. Diametrically opposite loops i1 and 18 are suitably fastened to the rotor casing ID at right angles to the inner trunnions l2 and I3 and other loops l3 and 2B are fastened to gimbal ring II at right angles to outer trunnions l4 and I5 for a purpose to presently appear.

A suitable gyro cage is now provided which comprises a pair of caging bails 2| and 22 loosely mounted upon outer trunnions l4 and 15 between the gim-bal ring and the fixed support, generally represented by the supporting bearing surfaces of Figure 1. In actual construction, bails 2| and 22 are mounted upon sleeves 2|a and 22a, respectively (only one set of these sleeves being shown), which are journalled within the instrument housing. The sleeves, in turn, carry bearings (not shown) for mounting therein trunnions l4 and i5 in such a manner that undesirable precessing torques are prevented from being generated upon the gyro during relative movement of the bails and trunnions l4 and I5.

Bail 2| is provided at its central base portion with a bracket 23 having a notched portion 24 and projecting outwardly from the bracket are two curved arms 25 and 28. Bail 22, like bail 2|, is also provided with a bracket 21 which has a notched portion 28 facing and corresponding to notched portion 24 of bracket 23. Ball 22, furthermore, is provided with two curved arms 29 and 30 formed integrally with or secured to bracket 21 in the same manner that arms 25 and 26 are secured to bracket 23. The free ends of arms 25, 2G and 29, 3a are curved slightly-toward caging pin it so that in an uncaged position (see Figure 2) the four arms together define substantially a circular stop which is adapted to engage the caging pin anywhere throughout 360 either when the gyro-rotor is at rest with its spin axis in some position other than the normally vertical position or when the gyro has precessed abnormally. The dotted linepositions of pin l6, indicated in Figure 2, show some of the possible positions of the pin prior to caging. The four curved arms are provided for the reason that without them, at any relatively large deviation of the rotor spin axis, the bails alone would be moved to a caged position without intercepting the rotor pin, and hence, would fail to centralize the gyro rotor.

In the position illustrated in Figure 1, bails 2| and 22 are shown to have been actuated by the novel apparatus of the present invention, to be described more fully hereinafter, into their operative or caged position wherein pin it has been engaged by one of the four arms and brought to a central and locked position within the two notched portions 24 and 28 of brackets 23 and 21. In their uncaged or inoperative position the bails are swung into a substantially horizontal plane, that is, bail 22 is swung forwardly 90 about the outer 'trunnions while bail 2| is swung rearwardly 90 about the same trunnions (see Figure 2). It

have completely overlapped arms 29 and 30.

The novel apparatus of the present invention for actuating the gyro cage, comprising bails 2| and 22, consists of a power circuit including a motor for winding a caging spring, the spring being held in a loaded or wound condition until the occurrence of a given predetermined condition when the spring is released to unwind and its force is expanded through a suitable gear train to drive the caging bails and their respective arms from the inoperative position of Figure 2 to the operative position of Figurel.

The power circuit comprises a. suitable energy source 3| which, in the case of an electrically driven gyro, supplies current to the gyroscope through suitable leads A and brushes, shown schematically in Figure l, in a well known manner. One side of source 3| connects by way of a lead 33 to one side of a motor 32 and with the other side of the motor by way of a remote manual uncaging control. The manual uncaging control comprises a slidably mounted knob 34 wh|ch is normally held by way of a spring 35 in a circuit caging position, illustrated by the dotted line position of Figure 1. Knob 34 has fastened thereto but insulated therefrom a pivoted contact bar 33, the latter being adapted, when the knob is pulled outwardly to the full line or uncaging position of Figure 1, to engage a stationary contact 31. Contact bar 36 connects electrically with a coil or solenoid 38 which, by way of a lead 33, is connected to the other side of source 3|.

A latching device is provided for holding knob 34 in the uncaged or outward position and comprises a pivoted lever 40 inductively coupled with solenoid 38 and normally urged by a spring 4| to the dotted line or unlatched position of Figure 1. Upon energization of the solenoid, such as, when the knob is pulled downwardly to bring contact bar 36 into engagement with contact 31, lever 40 is swung to the right to engage a slot 42 formedin the knob to hold the latter in the uncaged position.

A suitable lead 43 connects stationary contact 31 with a contact element 44 which, together with a second contact element 45, is mounted by means of an insulating block 43 upon a plate 41. Contact element 45, furthermore, connects with the other side of motor 32 by way of a lead 48.

Contact elements 44 and 45 engage a circuit bridging element 43 which is secured to a shaft 50 carrying a gear 5| thereon. The circuit bridging element, better shown in Figure 3, is provided with a conducting segment 52 throughout approximately 345" thereof while the remaining portion is composed of a non-conducting surface 53.

Bridging element 49 is rotated with shaft 50 by gear 5| which, in turn, is driven by motor 32 through a speed reduction gearing. To this end motor 32 is provided with a driving shaft 54 having a pinion 55 secured thereto. The speed reduction gearing comprises a gear 56 meshing with and driven by pinion 55 and provided with a pinion 51 which drives a second gear 53. A pinion 53 is secured for rotation with gear 58 and meshes with and drives a third gear on having a pinion 5| for driving gear 5|. The speed reduction gearing is so designed that the bridging element is always driven an angular amount to presently appear.

Gear Bland pinion 6| are secured'to a shaft 62 which is rotated during rotation of gear 80 by motor 32. A caging spring element 63 is sleeved reverse rotation stop 81, because of the engageabout shaft 62 and is secured to the shaft at its innerend and anchored at its outer end to the bottom of a plate 64 arranged parallel to and spaced apart from plate 41. The driving force of spring 63 is transmitted to bails 2| and 22 by means of a helical gear 65 secured to shaft 82 which is under the influence of the spring. Helical gear 65 meshes with and drives two helical gears 66 and 6'! which are mounted upon parallel shafts 58 and 69, the free ends of which carry gears it and H thereon; Gears 10 and H drive gears 72 and 13 which cooperate with toothed sectors 14 and I formed with the balls to move the letter when the spring is winding or unwinding.

It will be shown hereinafter that subsequent to a caging operation, with spring 69 unwound 7 and bails 2| and 22 in the position of Figure 1,

contact elements 44 and :35 will be in engagement with conducting segment 52 of the circuit bridging element 49. To energize the power circuit, therefore, knob 92 is pulled outwardly to engage contact bar 36 with contact 31 whereby motor 92 is connected across source 9i and drives the speed reduction gearing until non-conducting surface 53 of the bridging element engages contact element d5 to break the circuit and deenergize the motor. During actuation of the speed reduction gearing, shaft 62 has been rotated to wind spring 69 to place it in condition for a subsequent caging operation.

Means are provided to lock the spring in its wound position to prevent it from unwinding and moving bails 2| and 22 downwardly until certain desired and predetermined conditions exist. To this end a shaft 16, which carries thereon gear is and pinion 51 of the speed reduction gearing, is provided with a pawl element Ti, as better shown in Figure 4. Mounted on plate it is a bracket 78 which pivotally supports therein a lever 79 having a transverse arm 80 secured thereto or formed integrally therewith for cooperation with pawl ll.

The free end of lever 19 is secured within a bifurcated collar 8!, the latter being carried by a rod 82 which-projects below plate B l by virtue of an aperture 89 provided in the plate for that purpose. A spring element 86 connects lever l9 adjacent collar 8| to plate 66 and tends to maintain arm 80 above pawl 17 to permit spring 63 to unwind. Normally, however, spring 89 is not ment of abutment 88 with abutment 89, engages and holds pawl'l'l and shaft" against rotation, thereby defining a lock for spring. to prevent its unwinding.

Trigger 85, provided for normally holding rod 92 in position to maintain arm 80 and, therefore,

' stop member 81, in engagement with pawl ll,

has formedtherewith a ball swivel 9! which mounts the trigger for universal movement within a socket 92 formed in a third plate 93,. the latter being arranged below and parallel to plates '41 and 64. Furthermore, trigger 85 is centrally arranged so that normally its longitudinal axis is coaxial with the normally vertical gyro spin axis. A resilient spring 94 arranged about trigger 95 is secured at one end to plate 99 and at its other end to the trigger so that when the trigger is unrestrained it will always be brought to its normally vertical position in the path'of rod 82.

Under certain conditions trigger 85 is mechanically unseated to permit spring to to swinglever l9 and rod 82 into an extreme downward position wherein arm 30, together with stop member 81, is lifted away from pawl 11 to release spring 63 to cage the gyro in a manner to presently appear. When, subsequent to a caging operation, motor 32 is energized to wind spring 63 to uncage the gyro, such action, of itself, will not operate rod 82 and lever 78 to position arm 80 and sto 81 to engage pawl l1 and hold the spring in its wound condition. For thi reason a gear 95, mounted upon a shaft 96, is provided which meshes with gear 5! to be driven with the latter by the motor through the speed reduction gearbetter shown in Figure 4, a cam 91 is pivotally mounted on the bottom of gear 95 by way of a pin 98 while a spring 99, anchored at one end' to the gear is fastened at its other end to the free end of cam 91. A second pin I06, carried by the gearadiacent to the cam, is arranged in such a manner that cam 91 may pivot about pin 98 in a clockwise direction against spring 99 but cannot pivot in a counterclockwise direction. With the spring 63 wound to its maximum capacity, gear 95 is rotated sumciently to cause cam 9! to pass over arm 80 to urge the arm downwardly and, simultaneously therewith, rod 82 is lifted and trigger 85, by virtue ofspring 96, is centralized to engage and hold rod 82. At this point,

" shaft 16 continues rotating and for each revolupermitted to swing arm 80 to the unlocked position because the bottom of rod 82 is engaged and limited against downward movement by a trigger 85. In being so limited, rod 82 holds lever E9 in such a manner that one end of transverse arm 89 rests in the path of pawl 11.

The part of arm 80 immediately adiacentpawl 11 is provided with a'recessed portion having pivotaily mounted thereon, by way of a pin 86, a stop member 87 (see Figure 4). Member 8? is tion pawl Tl trips member 81 until motor 32 is de-energized'at which time shaft 16 is rotated in a reverse direction until pawl 11 engages and is held by stop member 87.

To the end that trigger may be mechanically unseated, a suitable solenoid ml is provided which is mounted upon plate 93 and is provided with a core or plunger I02 which pivotally supports at its free end a lever I03. Lever I03 is secured to a collar I09 mounted upon a shaft H15 rotatably Journalled within plate 93 and provided at its lower extremity with a trip pin I06 adapted, when the solenoid is de-energized, to engage and trip trigger 85 from its normal position shown in Figure 1. A resilient spring lfl'L'anchore'd at one end, connects with plunger ill? to urge it outwardly when the solenoid is de-energized.

Solenoid llll connects with one side of source 3| through a suitablelead I08 and with the other side of the source through a lead 809, a stationary contact llll, a pivoted contact her HI, and a lead 2. Contact bar I is shown in its normally closed position and its free end is connected to and insulated from a slidable control knob II3. In such position solenoid l8I always is energized so that plunger I82 is urged inwardly against the action of spring I81 to urge trip pin I86 away from trigger 85.

Plates 41, 84 and 33 are parallel to and spaced from each other and are fastened to a stationary part of the casing forming the bearings for supporting trunnlons I4 and IS. The plates, furthermore, define bearing and supporting surfaces for the various elements of the apparatus above described and have been shown in section only for a better understanding of the present invention.

The novel caglng and uncaging apparatus above described is adapted to operate in four distinct manners. It will act to cage the gyro automatically in case of a power failure or when the craft exceeds a predetermined angle of bank or pitch and it may .be remotely controlled by a manual operation to cage as well as uncage the gyro. Each method of operation will be described hereinbelow.

Operation #1 For purposes of clarity, it may be considered that the gyro is in a caged position and that knob 34 is pulled outwardly to the full line position of Figure l to uncage the gyro. Contact bar 38 is brought into engagement with stationary contact 31 whereby motor 32 is energized and winds spring 63 through the speed reduction gearing system, raising bails 2I and 22 to the position of Figure 2, until non-conductor portion 53 of circuit bridging element 49 engages with contact element 45 to break the circuit and de-energize the motor. At the same time, solenoid 38 is deenergized so that spring 4! swings lever 48 to the left or dotted line position of Figure 1 and spring 35 snaps knob 34 inwardly to disengage contact bar 38 from stationary contact 31. Just previous to the time that the non-conductor portion 53 of the circuit bridging element comes into engagement with contact element 45 to break the circuit, cam 91 engages arm 88 to urge stop 81 into the path of pawl 11. Simultaneously therewith, spring 94 centers trigger 85 to reset, and hold rod 82. As non-conductor portion 53 of element 49 engages contact element 45, the motor is de-energlzed and pawl 11 is rotated in a reverse direction to engage and be held by stop member 81, in which position spring 83 is locked against unwinding. Thus, the complete mechanism is in condition for an automatic caging operation upon the occurrence of predetermined conditions.

With the gyro rotor driven either pneumatically or electrically, it now may be assumed that the craft, and thus, the gyro supporting structure has been subjected to a predetermined angle of bank or pitch. With a predetermined angle of craft bank, depending upon the direction thereof, either loop I9 or 28 of gimbal ring II will engage and trip trigger 85. Should, on the other hand, the craft be subjected to a predetermined angle of pitch, depending upon whether it be climb' or dive, either loop I1 or I8 of rotor casing I8 will engage and trip the trigger.

Whichever loop engages and trips trigger 85, rod 82 is released and urged downwardly by spring 84 thereby pivoting lever 19 to swing arm 88 and stop member 81 from the path of pawl 11 so that spring 83 is free to unwind and rotate shaft 62. Bails 2| and 22, therefore, are lowered to engage and centralize caging pin I8 to cage the gyro by that solenoid I8 I virtue of the driving connection between helical gear 88 and bail sectors 14, 18 through gears 18, 1|; 12, 13 and helical gears 88, 81. In addition to driving bails 2| and 22 to their caged position, expanding spring 83 will also cause reversed rotation of the gear train so that non-conductor portion 83 will be rotated clockwise to almost engage contact element 44, leaving both contact elements 44 and 45 in engagement with the c'onducting portion 52 of bridging element 49.

Operation #2 The second operation consists in remotely uncaging the gyro when the undesirable flight condition has ceased to exist. To this end, knob 34 is pulled downwardly to bring contact bar 38 into engagement with stationary contact 31 so that motor 32 is energized to drive the speed reduction gearing. Solenoid 38, being energized, swings lever 48 to the right'to engage slot 42 and lock knob 34 in its uncaging position.

Shaft 82 is rotated through the speed reduction system to wind spring 83. Cam 81 is moved with gear 35 until it passes over arm 88 and since gear is rotating clockwise (Figure 4) stop pin I88 prevents arm 88 from swinging cam 91 out of the way about its pivot 38. Hence, cam 81 urges arm 88 together with stop 81 into the path of pawl 11. At this moment spring 94 centers trigger .85 to engage and reset rod 82. As the spring is being wound, pawl 11 travels in a clockwise direction with shaft 18 and engages and pivots stop member 81 about its pivot 88 once for every revolution of shaft 18.

With continued rotation of motor 32, non-conductor portion 53 engages contact element 48 to open the circuit and de-energlze the motor. With motor de-energization, solenoid 38 is de-energized and lever 48 is swung to the left by virtue of spring 4|. At the moment motor 32 is de-energized, spring 83, being in its maximum wound condition, starts to rotate shaft 82 in an opposite direction until pawl 11 engages stop 81 The latter cannot pivot away from pawl 11 because abutments 88, 88 engage so that the spring is locked and the complete apparatus is in condition for a subsequent caging operation.

Operation #3 In the event of a power failure at source 3|, when the gyroscope is connected electrically thereto and driven thereby, it is desirable to cage the gyro so that undue gyro precession and consequent bearing damage will be prevented. Also,

the gyro upon the occurrence of a power failure either at the source or within the circuit.

Under normal operating conditions, knob H3 of the caging circuit is inits full line closed position of Figure 1 so that solenoid IN is energized by virtue of its connection across source 3| to hold plunger I82 inwardly and trip in I88 away from trigger 85.

With the gyro connected to supply source 3|, any failure at the source to supply current to the gyro causes a like failure in the caging circuit so is tie-energized whereupon plunger I82, under the influence of spring I81, swings trip pin I88 to displace and unseat trigger 85 against the action of spring 94.

Rod 82, no longer held in place by trigger 88,

the circuit to solenoid NH. 7

tie-energized so that plunger. W2 is swung out:

is urged downwardly by spring 84 to raise arm 80 and stop member Bl away from the path of pawl Tl. Spring 83 is free to unwind and rotate shaft 82 which, through ball sectors N, I5 swings balls 2! and 22 to engage and center pin I8 to cage the gyro. As the gyro is caged, the speed I reduction gearing brings non-conducting portion 53 of bridging element 49 almost into engagement with contact element at.

The whole apparatus is now in the caged condition as that described in connection with Operation No. 1. Once the power failure has been remedied, knob 36 is pulled downwardly'to close the circuit to the motor to thereby wind spring tit and lift bails 2i and 22 to uncage the gyro in the same manner as that described in connection with Operation No. 2.

The automatic caging operation because of a power failure is somewhat different from the above in the case of a pneumatically driven gyroscope. With a power failure in either a pressure or suction pump used for pneumatically driven gyroscopes, the gyro on losing speed will process in such a manner that the loops of one of sets ll, it or G9, 2t will engage and trip trigger 85. Release of rod 82 initiates the caging operation in the same manner as that described in connection with Operation No. 1 or when the solenoid it! has been tie-energized as described in connection with Where neither abnormal flying conditions n'or power failure occurs, it may, nevertheless, be desired to manually cage the gyro. The apparatus thus far described is adapted to cage the gyro automatically but not by remote manual control.

Knob i 83 is provided for this purpose and when it is desired to remotely cage the gyro by manual control, the knob is pushed inwardly to the dotted line position of Figure 1 wherein contact bar iii is disengaged from stationary contact I Hi to break The solenoid is thus' wardly by spring iii? to cause trip pin are to engage and trip trigger 85. The subsequent operation of the apparatus to unlock spring 63, permitting it to unwind, and lower bails 2i and 22 to cage the gyro is the same as that described in connection with Operation No. l and Operation No. 3.

' It will now be apparent to those skilled in the art that a novel and desirable caging mechanism has been provided which acts to cage the gyro automatically during either abnormal flying conditions or during a power failure. The novel mechanism, furthermore, may be actuated by means of a remote manual control and after either of the automatic caging operations or the manual caging operation, the gyro may be uncaged by a remote manual control.

Although only a single embodiment of the pres ent invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as will now be understood by those skilled in the art. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

I I claim:

1. In combination with a gyro-vertical having a rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, an automatically operated cage for centering said casing with re spect to the support, a resilient controller for said cage, means comprising a device for mechanically locking said controller against operation, and.

and operating said locking means to release said controlling member.

3. In combination with an artificial horizon having 'a rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centralizing and locking said casing about said two axes, a controller for said cage, locking means for normally restraining operation of said controller, and means comprising a control circuit for engaging and releasing said locking means.

4. In combination with an artificial horizon having a rotor provided with a casing and an spin axis and a rotor casing mounted for freedom about two mutually perpendicular axes other than said spin axis, comprising acage for centralizing and locking said casing about said two axes upon the occurrence of a predetermined condition, a normally wound resilient member for operating said cage, locking means normally holding said resilient member against unwinding, means operated by the occurrence of said condition for engaging and releasing said locking means wherei by said cage is operated, and control means for winding said resilient member and operating said cage to an uncaging position.

6. Caging mechanism for a gyroscope having a rotor provided with a normallyvertical spin axis and a rotor casing mounted for freedom about two mutually perpendicular axes other than said spin axis, comprising a cage for centralizing and locking said casing about said two axes, a normally wound resilient member for operating said cage, means normally holding said resilient member against unwinding, a control circuit including means for engaging and releasing said holding means whereby said cage is operated, and means connected to said circuit for winding said memiber and operating said cage to an uncaged posiion.

7. Cagin mechanism for a gyroscope having a rotor provided with a normally vertical spin axis and a rotor casing mounted for freedom about two mutually perpendicular axes other than said axes, a cage for centralizing and locking said casing about said two axes, a wound sprlngfor driving said cage, locking means normally holding said spring against unwinding, means comprising. a control circuit for operating said cage to an uncaged position and for winding said spring, a current source included in said circuit and supplying current to said rotor, and means responding to a power failure at said source for engaging and releasing said locking means whereby said spring operates said cage to cage and lock said casing about said two axes.

9. In combination with a gyro vertical having an electrically driven rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centering said casing with respect to the support, actuating means for said cage, means comprising a trigger for normally holding said actuating means in an inoperative condition, means brought into operation upon a predetermined relative tilt of said casing and said support for actuating said trigger to release said actuating means whereby said cage centers said casing, a control circuit including a motor for energizing said actuating means and operating said cage to an uncaged position whereupon said trigger holds said actuating means against operation, a current source included in said circuit and supplying current to said rotor, and means automatically responsive to a power failure in said circuit for actuating said trigger to release said actuating means whereby said cage centers said casing.

10. In combination with a gyro-vertical having an electrically driven rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centering said casing with respect to the support, actuating means for said cage, means comprising a trigger for normally holding said actuating means in an inoperative condition, means brought into operation, upon a predetermined relative tilt of said casing and said support for actuating said trigger to release said actuating means whereby said cage centers said casing, means comprising a control circuit for energizing said actuating means and operating said cage to an uncaged position whereupon said trigger holds said actuating means against operation, 2. current source included in said circuit and supp y ng current to said rotor, means including a solenoid operated trip member for said trigger connected in said circuit, and manually operative controlling means in said circuit for operating said trip member to actuate said trigger whereby said actuating means is released to operate said cage to center said casing. i

11. In combination with a yro-vertical having a rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perp ndicular axes, an automatically operated cage for-centering said casing with respect to the support upon the occurrence of a predetermined condition, actuating means for said cage, means comprising a trigger for holding said actuating means in an inoperative condition, and means brought into operation in response to the occurrence of said condition for actuating said trigger to release said actuating means.

12. In combination with a yro-vertical having a rotor provided with a. casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, an automatically operated cage for centering said casing with respect to the support upon the occurrence of a predetermined relative tilt of said casing and said support, actuating means for said cage, means comprising a normally resiliently centered trigger for holding said actuating means in an inoperative condition, and means brought into operation in response to the occurrence of said predetermined tilt for displacing said trigger to release said actuating means.

13. In combination with a gyro-vertical having a rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centering said casing with respect to the support and normally maintained in an uncaged position, actuating means for said case. means comprising a normally resiliently constrained trigger for bolding said actuating means in an inoperative condition, and a control circuit including manually operative means therefor for displacing said trigger to release said actuating means.

14. In combination with a gyro-vertical having an electrically driven rotor provided with a casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centering said casin with respect to the support and normally maintained in an uncaged position, actuating means for said cage, means comprising a normally resiliently constrained trigger for holding said actuating mean in an inoperative condition, and means automatically operative in response to a power failure at a current source supplying said rotor for displacing said trigger to release said actuating means.

15. In combination with a gyro vertical having a rotor provided with a rotor casingand an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage for centralizing said casing with respect to the support, means comprising a rotatable driving member for driving said cage, a, locking mechanism normally restraining operation of said driving means, and means actuated by a predetermined relative tilt of said casing and said support for engaging and releasing said locking mechanism.

16. In combination with a gyro vertical having a rotor provided with a rotor casing and an outer support mounting said casing for freedom about two mutually perpendicular axes, a cage'for centralizing said casing with respect tothe support,

' means comprising a rotatable driving member for 

